Research On The Motion And Heat Transfer Of Ash In Rotary Ash Coolers

Roller ash cooler has been widely applied in the C irculating fluidized bed boilers due to its wide adaptability, simple structure,high reliability. At present,for the design and reconstruction of roller ash coo ler is still by the experience,analysis of the ash movement and heat transfer characteristics are rare.The mathematical model of the mean residence time of the ash rolling process in the rolling-cylinder type slag-coole is established,using the particle trajectory model and considering the ash fall time, at the same time gives a simplified calculation formula of mean residence time, comparied and verified with the previous models,and using the model to investigat the relationship between drum diameter,the speed of roller,the roller angle,the ratio of slag bed height to cylinder diameter(0h R)and the ratio of the fall time and the total time(gunp). The result shows that this model is more accurate;the increaseing of drum diameter, the speed of roller, the roller angle, or the reducing of 0h R can improve the value of gunp, which greatly influenced by the roller diameter and the rotational speed of cylinder.Heat transfer calculation model is established considering the ash axial heat conduction. By calculating the heat transfer of ash which considering the axial heat conduction of ash and ignoring the axial heat conduction, the results show that: ash from the roller ash cooler inlet to exit, in considering the axial heat cond uction, along the axial direction, the ash temperature which considering the axial heat conduction of ash is lower the ash temperature which ignoring the axial heat conduction of ash. The temperature gradient considering the axial heat conduction of ash is larger than the temperature gradient ignoring the axial heat conduction at the inlet of the roller ash cooler. At the exit of the roller ash cooler. However, the temperature gradient near the slag cooler outlet is opposite. The heat transfer model considering the axial heat conduction of ash is used to investigate the influence factors of axial heat conduction of ash. It turned out that: at the same location along the axial of roller ash cooler,the increase of ash filling rate or roller diameter or the increase of the angle between the surface of ash and the center of the roller makes the ratio of the axial heat conduction and the heat release of ash increase. At the inlet of the roller ash cooler, this characteristic is obvious.Finally, the method of dividing the inlet section and the convection section is proposed to simplify the calculation of heat transfer.